Tanks for holding liquids such as water and oil have traditionally been formed of vertical wooden boards pulled into a cylindrical shape by horizontal outside tension bands. The bands have been tightened to the point of crushing the adjoining edges to prevent leakage.
The usual wooden vertical tank board has a horizontal width that is two or at most three times the thickness of the board to avoid vertical cracks. When water or other liquid is placed in the tank, the hydraulic pressure forces the wooden boards outwardly and the steel circumferential bands must be tightened again until the bands cut deep enough into the edges of the wood boards to counteract the outward force of the water or other liquid. While it is possible to shape the outer surface of the boards with the arc of the finished cylindrical tank, this is expensive and seldom done. Instead, commercially available flat boards are used.
There has been a great need for a waterproof tank that can be quickly assembled and which is free from leakage.